1. Field of the Invention
The present invention relates to an ophthalmologic apparatus, a control method, and a program.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2009-268772 discusses automatic focusing system using a positional relationship between two focus index images obtained by return light of divided focus indexes projected onto a fundus of a subject's eye.
If a subject's eye is highly myopic (near-sighted) or highly hyperopic (far-sighted), it is known that a diopter correction lens is inserted into an observation imaging optical system. When the diopter correction lens is inserted, an optical characteristic of the observation imaging optical system changes, and an optical relationship between a focus index projection unit and the observation imaging optical system changes. Therefore, focus detection using above-described focus index images becomes difficult.
On the other hand, Japanese Patent No. 4744973 discusses an ophthalmologic imaging apparatus capable of performing automatic focusing even after a diopter correction lens is inserted using a focus detection method utilizing a contrast of a focus index or the like.
However, a period of time required to perform focus detection based on the contrast becomes longer than that when focus indexes are used, until focusing is completed, because the focus detection based on the contrast has to search for a position where an evaluation value becomes a peak while driving a focusing lens.